1. Field of the Invention
The present invention relates to a leveling pole or rod generally used together with a surveyor's level for measuring a difference in elevation between two points positioned on the ground.
2. Description of the Related Art
In surveying, a level (surveyor's level) is used when a difference in elevation between two points (surveying points) positioned on the ground is to be measured. In general, the level is placed at one of the two points and a leveling pole bearing a scale thereon is placed at the other point. Under this condition the horizontal hairline (reticle) of a telescope provided on the level is set to be real horizontal (i.e., horizontal with respect to gravity) to serve as a reference line to read the scale on the leveling pole, so that the difference in elevation between the two points can be measured based upon the value read from the scale.
A level having a leveling bubble, and an auto-level are both widely known. In the auto-level, the horizontal hairline thereof is automatically set to be real horizontal even if the level is placed on the ground with the horizontal hairline initially being inclined to some degree from the real horizontal.
A level having a telescope provided with an autofocus system has recently been proposed. For instance, an auto-level having a telescope provided with an autofocus system (hereinafter referred to as an "AF auto-level") has been proposed in U.S. patent application Ser. No. 08/579 240, filed on Dec. 28, 1995.
With such a type of AF auto-level, a surveyor does not have to manually focus the telescope of the AF auto-level on a leveling pole, but only has to orient the telescope toward the leveling pole, so that the telescope can automatically focus on the leveling pole.